Every place that sells Eagle cast ("the 360400" like part number)says in the ad is external balance, but any crank can be internally balanced. The forged are more dense so that usually equates to an internal balance as the crank counterweights are as heavy or heavier than the reciprocating weight, the cast are lighter so you need to add weight with weights on the flex/flywheel and/or balancer. This is ASSUMING that you are using stock weight pistons and rods. Most stroker pistons are shorter, hence lighter than stock pieces (which are heavy from the factory) so the "adding weight to balance" is misleading if you are using non factory weight parts. Heavy forged pistons require heavy metal to be added to the counterbalance to counterbalance the crank. If you go lighter, and who doesnt these days, you end up taking metal away (drilling) from the counterbalance. I got an Eagle cast 360400 crank and am using stock 360 rods and MP cast stroker pistons for a mild build (and cheap I may add) I did the calculations and weights with a digital .01g resolution scale with a shop buddy and took about 8g off each rod and equalized everything (pistons, rods, pins)to .5g and the cast crank balanced on the machine to within +15g or so and the guy says youll probably pick that up in oil anyway. He was very suprised how close we got it and that was just going off the published bobweight of the crank. He also told me that press fit pins can be shortened if you couldnt take any more meat off the pistons or rod little end (trying to lighten aluminum pistons grams at a time, you run out of meat pretty fast) as the pins are rather heavy items and even 1-2mm of an end is measurable weight when you are looking at g's.

I remember seeing a SCAT lightened crank that was using LY rods and forged 440 pistons, that crank had about $500 in mallory slugs in its counterbalances to make it work with the heavy reciprocating weight. IIRC, Mopar "detroit" balanced the 360 with the balancer and convertor/flywheel attached, so you cant get away with one or the other has to be both if getting a 360 crank. all other LA's(not cast 73 340) were neuteral balanced, as they all should have been, and that is because the cast 360 was using the 340 rods (heavy)without the hole drilled in the (lightened) rod journal, ala forged 340. Its a black art indeed.

No I've just been wrestling with this for a week, I've not taken the task of dropping the trans just to switch a plate and find out. It's just been adding the weights, removing, them over and over and seeing what it does. I called shop tonight and they are getting lies from the crank shop saying they marked the weight that was needed, I have the weights and nothing is marked. It's about to come out for a stock motor. Because this is getting worse every day.

This is from the Eagle webs site under Chryser 4" cast crank specs:

- 4.0000 103604000 cast internal bal. bob weight 2050
HP rating 500

Perhaps the reason that some shops say its for "external" balance is the same reason you are having issues now....they are clearly confusing the 360 factory replacement crank (which Eagle says IS made for an external balance).......with the cast stroker item.

FWIW - the Cast = external vs forged = internal theory doesn't work

- Myself and several others I know run the Cast 340 4" crank and ALL have been internally balanced with very little metal needing removal..and NONE needing additional metal. (This is using KB slugs and eagle rods.)

I agree with CJK - Strip the flex plate and damper and use a neutral assembly - hopefully they haven't butchered your crank completely....if they did anything at all?

Like I said, my 408 with eagle cast 360 style crank was internally balanced. I have sir rods and kb forged pistons. I use a neutral flywheel and balancer. Why would I lie about it?I had it balanced but I put everything together myself.


Don't pull your hair out. Just pull the transmission and change out the flex plate. If you wanted your hands to stay clean you would drive a new Honda civic, right? That's why we do this stuff, isn't it? It will make the ride that much sweeter after you go through all this crap. My stroker is tons of work but so much fun. It's totally worth the trouble.

Good luck

rdr

bringing this back from the dead...Why do you suppose they use 1 piston /pin but use 2 rods weights when figuring the bobweight? And do they measure the big and little ends using the other ends centerline as the pivot?

Because the formula is all of the big end weight and half of the small end weight. This isn't derived by any mathematical formula, it's an empirical fix derived over the years.
Yes, they measure the weight of the big end of the rod and the small end of the rod with the centers of the two holes level.

If you really want to get confused, delve into the subject of underbalancing and overbalancing.

I wonder what a supercomputer simulation would find is the ideal balance. One could run countless iterations in cyberland.

R.

https://board.moparts.org/ubbthreads/show...e=0#Post8189223

looks like another one bit the dust....

Wondered when that was going to come up....
R.

That crank didn't owe me anything. I beat the crap outta it for years with a stick shift, occasional slicks, and lately a high winding cam.

Did I learn my lesson? Yep. But it was a ton of fun while it lasted!

Sunday I am throwing the block on a stand- I'll share some pics then. Goin scat next time!

And I'm not sure why you brought this thread back? Before I broke I was shifting at 5-6k for years with no freaky vibes or anything. I had built a bunch of bike motors and this was my 1st v8. I beat up a ton of subarus and hondas while flying the mopar flag with my little $5000 backyard hotrod driveline!